Method of setting the twist in twisted



nited States Patent METHOD OF SETTING THE TWIST IN TWISTED YARNS Leo J. Novak, Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, @hio, a corporation of Ohio No Drawing. Application June 18, 1953,

Serial No. 362,666

6 Claims. (Cl. 117-139.5)

This invention relates to yarns and to the method of processing them, and is of particular advantage in the processing of natural silk and synthetic yarns to facilitate handling thereof in the manufacture of fabrics, especially the fabrication of hosiery by knitting.

Many problems arise in the processing and handling of natural silk and synthetic yarns. The successful manufacture of many fabrics depends on the use of twisted yarns. This involves the problem that natural silk and synthetic yarns, being characteristically inherently resilient, tend to return to their normal condition after being deformed and thus when such yarns are twisted to the desired number of turns per inch they tend to return to untwisted condition when the twisting or deforming stress is removed. Another problem, encountered more particularly in fiat-knitting synthetic yarns of the polyamide (nylon) type, is that, normally, when such yarns are knitted into sheer, full-fashioned stockings and subsequently handled, the stockings develop an undesirably large proportion of pulled threads. A further problem is that fabrics knitted from natural silk and synthetic yarns, particularly the latter, exhibit a decided tendency toward edge-rolling which makes the looping and seaming operations very difiicult and tedious.

It has been proposed to minimize the tendency of the twisted yarns to untwist, by subjecting the yarns to various methods of twist-setting such as heat, steam, water, water vapor, sizing, etc., or combinations of these methods. Methods utilizing heat, steam or hot water depend on the activation of the yarns to plastic condition in which they are readily deformed but require careful control to avoid activation of the yarn to a condition of controlled softness without flow of the resin or the like and loss of identity of the filaments and yarns. Various sizing agents have been used more or less successfully but few of these perform the dual purpose of setting the twist and rendering the yarns snag-proof without causing the yarns to deposit excessive amounts of snag-proofing composition on the needles and sinkers of the knitting machine which result in irregular stitch formation.

One object of this invention is to provide twisted natural silk and synthetic yarns in which the tendency to untwist is eliminated or controlled.

Another object is to provide twisted natural silk and synthetic yarns set in the twisted condition and adapted to be knit into fiat, snag-proof fabrics which do not exhibit the tendency to undergo edge-rolling when the fabric is taken from the knitting machine.

Still another object is to provide a new means and method for setting the twist in twisted yarns and rendering such yarns capable of being knit into flat, stabilized snag-proof fabrics.

Other objects and advantages of the invention will appear hereinafter.

In accordance with the invention there are provided twisted yarns carrying a twist-setting film of an ester of a dextran or dextran conversion product with a saturated ice fatty acid containing between 8 and 18, preferably be tween 14 and 18 carbon atoms.

The dextrans are high molecular weight, branched polysaccharides made up of anhydroglucopyranosidic units joined by molecular structural repeating alpha-1,6 and non-alpha-1,6 linkages, at least 50% of the linkages being, apparently, alpha-1,6 linkages. The properties of the dextrans, including the molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios, the molecular weight, the water sensitivity and the osmotic pressure in liquids, vary.

Dex'trans may be obtained in various ways. They may be produced microbiologically, for example, by inoculating a nutrient medium containing sucrose, particular nirtogenous compounds and certain inorganic salts, with an appropriate microorganism, such as those of the Leuconostoc mesenteroides and L. dextranicum types and incubating the culture at the temperature most favorable to the growth of the particular microorganism.

In one method of obtaining a dextran to be esterified to produce the twist-setting agents of the invention, there is first prepared an aqueous nutrient medium of the following typical composition. 7

Percent by weight Sucrose 20.0

Corn steep liquor 2.0 Monobasic potassium phosphate 0.5 Manganous sulfate 0.002 Sodium chloride 0.50 Water Balance This medium is adjusted to a pH of between about 6.5 and about 7.5, preferably 7.2, and then sterilized. The material is cooled to room temperature and inoculated with a culture of the dextran-producing bacteria,

ferment to bring the pH thereof to about 7.0 to 8.0.

This aids in the precipitation of phosphates. Thereafter,

acetone or alcohol, which may be a water-miscible aliphatic, such as methyl, ethyl or isopropyl, is added in sufficient quantity to precipitate the dextran and this' brings down, with the dextran, occluded and adsorbedbacteria, and nitrogenous and inorganic elements. To occasion complete precipitation of the dextran it may be desirable to allow the mix to stand for a relatively long period, such as about 6 hours. The precipitated dextran may be dried in any suitable manner, for example, by drum drying, and the fluffy product thus obtained may be reduced to a powder.

A purer dextran may be obtained by adding an aliphatic alcohol to the fermented culture at a pH between 2.5 and 4.5. The precipitate thus obtained may be further purified by again precipitating it with the alcohol. Several precipitations may be performed.

The higher fatty acid radicals may be introduced into a dextran having a molecular weight between 5,000 and 50 (10 as determined by light-scattering measurements. Thus, the fatty acid radicals may be combined chemically with the native dextran described above or a dextran of similar higher molecular weight, or the dextran may have a lower molecular weight. The relatively low molecular weight dextrans may be obtained, for instance,

by hydrolysis of the higher molecular weight dextrans, as by means of acid or enzymatically. The hydrolyzed product may be fractionated, to obtain a dextran of more uniform or more nearly uniform molecular weight. The dextran may be treated by conventional techniques to remove pyrogens and coloring materials. The dextran may be a so-called clinical dextran, such as may be used as a blood plasma extender. One of the presently preferred twist-setting agents is a highly substituted palmitate or stearate derived from a native (unhydrolyzed) dextrau.

The dextran may be obtained by inoculating the culture medium with microorganisms other than that mentioned above. Thus, it may be a water-soluble dextran obtained by the use of the microorganisms bearing the followng NRRL classifications: Leuconostoc mesenteroides B419, 13-1146, 13-1190, or a water-insoluble or substantially water-insoluble dextran obtained by the use of Leuco'nostoc mesenteroides B-742, B-ll9l, 13-1196, 3-1208, 3-1216, Bl120, 13-1144, B523, Streptobaczerizm'z dextmnicum Bl254 and Betabncterium rcrmifol-me B-l139.

The dextrau is not limited to one prepared under any particular set of conditions, including the microorganism used. it may be produced enzymatically, in the substantial absence of bacteria, by cultivating an appropriate microorganism, for example, L ucoiwstoc mesenteroides 3-512 to obtain a dextran-produc'ing enzyme, separating the enzyme from the medium in which it is produced, and introducing the enzyme into a medium in which dextran is produced by the action of the enzyme. Also, the dextran may be obtained by bacterial conversion of 1,4 linkages of dextrin to 1,6 linkages of dextran. The dextran may be insoluble in water under ordinary conditions but soluble in aqueous alkali solution.

The higher fatty acid radicals may be introduced into the dextran molecule by an appropriate method, to produce the dextran fatty acid esters to be incorporated into the regenerated cellulose or similar fibers. The esters may be prepared by the methods described in the co pending application of Novak et al., Serial No. 351,743, filed April 28, 1953.

Thus, the dextran, in the form of a free-flowing white powder, may be reacted with an esterifying derivative of the higher fatty acid, and preferably a halide such as the chloride thereof, in the presence of an acid acceptor or binding agent such as an organic base, as for instance a heterocyclic tertiary amine of the type of quinoline, pyridine, N-methyl morpholine, etc. and in the presence of a substance in which the reaction product is at least partially solvated, that is dissolved or swollen, as it is formed during the reaction, which results in the reaction mass being maintained in a highly swollen or dissolved state and thus insures substantially uniform, homogeneous reaction between the dextran and the esterifying agent. Substantances which dissolve or swell the ester as it is formed are, for example, xylene, toluene, dioxane, etc. In general, the reaction may be carried out at temperatures between 100 C. and 155 C. for time periods varying inversely with the temperature between a half hour and three hours. The ester may be recovered from the crude reaction mixture by washing the latter with water to remove the hydrochloride of the organic base, removing the aqueous layer, adding a solvent for the ester to the residual mass, precipitating the solution into a non-solvent for the ester, such as a lower aliphatic alcohol, and filtering to obtain the ester.

Or the introduction of the higher fatty acid radical.- into the dextran molecule may be effected by reacting the dextran with the selected acid in the presence of an impeller which may be the anhydride of a monohalogenated monobasic organic acid, e. g., monochloro acetic anhydride, and an esterification catalyst such as magnesium perchlorate at temperatures at which the reaction mixture remains in the liquid state, in general in the range between 50 C. and 100 C. and for a time varying inversely with the temperature between one-half hour and two hours. The ester may be isolated from the crude reaction mass by cooling the mass, dissolving it in a solvent therefor, precipitating it into a non-solvent for the ester, and filtering the ester.

The higher fatty acids which may be used as esterification agent, in the free acid form or in the form of their chlorides, are those saturated acids containing from 8 to 18 carbon atoms and including caprylic, pelargonic, palmitic, margaric, and stearic acids, and the corresponding chlorides. Two or more of the substantially pure acids, or chlorides thereof, may be used, resulting in the production of mixed dextran esters. Or commercial acids, which comprise mixtures, may be used. For example, commercial or technical grade stearic acid, which comprises a mixture of stearic and palmitic acids, yields dextran stearate-palrnitate.

The D. S. (degree of substitution or ratio of fatty acid radicals to anhydroglusopyranosidic units of the dextran) may vary, and may be from less than 1.0, say up to about 20.0 or even higher, acid radicals per anhydroglucopyranosidic unit to about the possible maximum of 3.0 of the fatty acid radicals per anhydroglucopyranosidic unit. Such esters may be obtained by using the fatty acid or its chloride in amounts varying between less than 1.0, say 0.1 and 10 parts thereof by weight per part of dextran. Unlike the inherently hydrophilic dextrans from which they are derived, the fatty acid esters are resistant to moisture to an extent which depends on the D. 8., the higher the proportion of fatty acid radicals per anhydroglucopyranosidic unit, the greater the water resistance. The presently preferred twist-setting agents are the more highly substituted esters, e. g., those containing an average of between 2.5 and 3.0 chemically combined fatty acid radicals per anhydroglucopyranosidic unit of the dextran, and particularly those esters derived from the saturated acids of longer chain length, i. e., those containing from 14 to 18 carbon atoms. The esters are wax-like in consistency, form hard, firm but plastic or flexible films on the twisted yarns and have melting and softening points sufficiently high to withstand undue softening under the heat of friction generated during fabrication, as for instance during knitting, so that when the yarns are knitted, there is no tendency for the ester to deposit excessively on the needles and sinkers of the knitting machine, nor of the twist-set yarns to stick to the guides and snappers following a shut-down of the knitting machine and, consequently, no difficulty with press-01f when the machine is re-started.

Depending on the D. S., the esters may be applied to the twisted yarns from aqueous dispersions or emulsions containing effective dispersing or emulsifying aids, or from solutions. The preferred highly substituted esters are soluble in non-polar solvents such as'the halogenated hydrocarbons, e. g., chloroform and carbon tetrachloride,

the common aromatic hydrocarbons of the type of ben-' zene, toluene and the xylenes, and the Freons, these latter being commercially available chlorofluoromethanes of the type of Freon 11, a trichloro-monofluore-methane, and Freon 12, a dichlorodifluoromethane, and those solvents may be used. The esters may be used in varying amounts. Proportions thereof between 1 and 5%, by weight of the treating medium are satisfactory in most cases, but larger amounts up to 10% or even higher may be used if desired. The twist-setting media are applied to the yarns in any suitable way as by spraying, contacting the travelling yarns with a brush or roller partially immersed in the medium, propulsion of the treating medium through a wound supported or unsupported package of the yarns, such propulsion and distribution of the medium on the convolutions of the package being facilitated by carrying out the treatment in a field of high frequency sound waves. In a preferred embodiment, the yarn is advanced continuously through a bath containing the dextran ester and then through a drying zone. When solu- 5. tions of the ester in volatile solvents are employed, the drying may be under conditions such that the volatilized solvent is collected and condensed for re-use. The setting treatment is preferably performed immediately after twisting of the yarns and as the yarn proceeds from the stage at which it is given the desired number of turns per inch by suitable apparatus such as uptwisters or downtwisters.

The following examples, in which the percentages given are by weight are illustrative of specific embodiments of the invention, the details set forththerein not being limitative.

Example I An oriented continuous 10-filament, 30 denier nylon (polyhexamethylene adipamide) yarn with 30 turns of Z twist per inch is treated with a chloroform solution of dextran palmitate (derived from a native B-512 unhydrolyzed dextran and containing an average of 2.9 palmitoyl groups per anhydroglucopyranosidic unit), using a modified bobbin-to-bobbin type arrangement in which the yarn is drawn ofl? a spool through a pre-tension device, over a roll dipping in the twist-setting solution, passed through a drying zone, and wound up on a bobbin.

Example II A BO-denier, -filament, 30-turn regenerated cellulose yarn is treated with a 5% carbon tetrachloride solution of a dextran stearate (derived from a hydrolyzed B-5l2 dextran having an average M. W. of about 60,000 to 85,000 and containing an average of about 2.9 stearoyl groups per anhydroglycopyranosidic unit) by passing the yarn continuously through the solution and thence through a drying zone. Twist-set yarns carrying a pliable but firm film of the dextran stearate are thus obtained.

The amount of dried film-forming dextran ester on the yarn may vary within wide limits but the preferred amounts will lie within the range of 1% to of the ester based on the weight of the dried yarn. The take-up of ester by the yarn during the treatment will depend on several controllable factors including the concentration of ester in the bath and the rate of feed of the yarn therethrough or time of contact of the yarn with the bath. In a method in which the yarn is advanced through the bath, a speed of from 100 to 1,000 feet a minute and lengths of travel of the yarn in the bath between about 4 inches and 10 inches will be satisfactory.

The twist-setting media may be removed from the yarns, after fabrication thereof, by boil-off or scouring or by treating the fabric with a solvent for the ester. Where such solvents are used, the resulting solutions, after appropriate fortification, if necessary, may be used directly for applying the twist-setting ester to a fresh batch of twisted yarn.

The yarn may have any number of turns per inch and may be a high-twist yarn such as is used in the making of crepe fabrics. When such high twist yarns of regenerated cellulose are fabricated by weaving and the woven fabric is treated to remove the dextran ester and then wet-out, for instance in a hot liquid containing neutral wetting agents, or in an alkaline liquor containing sodium hydroxide, the yarns swell, shrink, and tend to untwist, resulting in interesting surface (crepe) efiects.

It will be apparent from the examples that the term synthetic yarns as used herein includes yarns of the regenerated cellulose type. All types of twisted yarns, especially yarns formed of continuous filaments may be processed according to the invention. The dextrari esters adhere firmly to yarns comprising the smooth, slick filaments.

The twist-set yarns may be fabricated by weaving or knitting. The yarns may be knit without deposition of the dextran ester on the elements of the machine, to produce fabrics which are substantially snag-proof and which tend to remain flat without rolling of the edges leading to seaming problems.

While the invention has been described in detail in connection with the use of the dextran esters as twistsetting media, it is within the purview of the invention to employ higher saturated fatty acid esters of dextran conversion products such as esters of partial lower acyl esters, partial ethers, and partially carboxyalkylated and hydroxyalkylated derivatives of the dextrans. Thus there may be used products which, in addition to the higher fatty acid radicals also contain acyl radicals of from l5 carbons, alkyl radicals of from 1-5 carbons, and carboxyalkyl and hydroxyalkyl groups in which the alkyl radical contains from 1 to 5 carbon atoms, such as carboxymethyl and hydroxyethyl dextrans. The carboxymethyland hydroxyethyl-substituted dextrans containing the chemically combined higher saturated fatty acid esters may be selected for more ready dispersibility in water when aqueous twist-setting compositions are preferred. Broadly speaking, these esters of the dextran conversion products may contain per anhydroglucopyranosidic unit an average of from less than 1.0 to 2.9, preferably to 2.5, of the radicals derived from saturated fatty acids of from 8 to 18 carbon atoms, and from less than 1.0 to 2.9, preferably to 2.5, of other radicals such as lower acyl, alkyl, carboxyalkyl and hydroxyalkyl. In a preferred embodiment, the esterified conversion products contain an average of from less than 1.0 to not more than 1.5 of the radicals other than the higher saturated fatty acid radicals and not less than an average of 1.5 of the higher saturated fatty acid radicals, the total number of substituent groups per anhydroglucopyranosidic unit being not greater than 3.0.

It will be apparent that a wide choice of specific twistsetting agents is possible by appropriate selection of the dextran, the esterifying acid, and the D. S. Therefore, it will be understood that while specific embodiments of the invention have been exemplified herein, it is not intended to limit or circumscribe the invention by the details given, since it is susceptible of various modificatons and changes which come within the scope of the disclosure and of the appended claims.

I claim:

1. A method of setting the twist in twisted yarns which comprises treating the twisted yarns with a liquid medium containing 1% to 10% by weight of a twist-setting agent consisting of an ester of dextran, containing initially at least some free hydroxyl groups, with a saturated fatty acid containing from 8 to 18 carbon atoms, and drying the treated yarns to thereby set the twist therein as a result of the presence of the twist-setting agent thereon.

2. A method of setting the twist in twisted yarns which comprises treating the twisted yarns with a liquid medium containing, as a twist-setting medium, 1% to 10% by weight of an ester of a dextran with a saturated fatty acid containing from 8 to 18 carbon atoms, said ester containing an average of from about 2.5 to 3.0 radicals derived from the fatty acid per anhydroglucopyranosidic unit, and drying the yarns to thereby set them in the twisted condition as a result of the presence of the solid twist-setting ester thereon.

3. A method of setting the twist in twisted yarns which comprises treating the twisted yarns with a non-polar solvent solution of 1% to 10% by weight of a twistsetting agent consisting of a dextran palmitate containing an average of from about 2.5 to 3.0 palmitoyl radicals per anhydroglucopyranosidic unit, and drying the treated yarns to thereby set them in the twisted condition as a result of the presence of the dextran palmitate thereon.

4. A method of setting the twist in twisted yarns which comprises treating the twisted yarns with a non-polar solvent solution of 1% to 10% by weight of a twistsetting agent consisting of a dextran stearate containing an average of from about 2.5 to 3.0 stearyl radicals per anhydroglucopyranosidic unit, and drying the treated yarns to thereby set them in the twisted condition as a result of the presence of the dextran stearate thereon.

5. A method of setting the twist in twisted yarns which comprises treating the twisted yarns with a non-polar solvent solution of 1% to 10% by weight of a twistsetting agent consisting of an ester of dextran with a saturated fatty acid containing from 8 to 18 carbon atoms, said ester containing an average of from about 2.5 to 3.0 radicals derived from the fatty acid per anhydroglucopyranosidic unit, and drying the treated yarn to thereby set them in the twisted condition as a result of the presence of the solid twist-setting dextran ester thereon.

6. A method of setting the twist in twisted regenerated cellulose yarns which comprises treating the twisted yarns with a non-polar solvent solution of 1% to 10% by weight of a twist-setting agent consisting of an ester of a dextran with a saturated fatty acid containing from 8 8 to 18 carbon atoms, saidester containingan average of from about 2.5 to 3.0 radicals derived from the fatty acid per anhydroglucopyranosidic unit, and drying the treated yarns to thereby set them in the twisted condition as a result of the presence of the solid twist-setting dextran ester thereon.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF SETTING THE TWIST IN TWISTED YARNS WHICH COMPRISES TREATING THE TWISTED YARNS WITH A LIQUID MEDIUM CONTAINING 1% TO 10% BY WEIGHT OF A TWIST-SETTING AGENT CONSISTING OF AN ESTER OF DEXTRAN, CONTAINING INITIALLY AT LEAST SOME FREE HYDROXYL GROUPS, WITH A SATURATED FATTY ACID CONTAINING FROM 8 TO 18 CARBON ATOMS, AND DRYING THE TREATED YARNS TO THEREBY SET THE TWIST THEREIN AS A RESULT OF THE PRESENCE OF THE TWIST-SETTING AGENT THEREON. 